The present invention relates to a communication control system. The present invention is applied, for example, in a mobile IP network environment configured by nodes each implementing a mobile IP (Internet Protocol), to a home agent (HA) or to a foreign agent managing a terminal-moved network of a mobile terminal (MN (Mobile Node)) and to the mobile terminal employed by a user.
Over the recent years, a research of the mobile IP defined as a technology for enabling the mobile terminal to perform continuous (seamless) IP communications without depending on its location, has been advanced.
The mobile IP has already been standardized in IPv4 (Internet Protocol version 4), wherein a great number of network products such as clients, routers and servers each implementing a mobile IP function have appeared. An active discussion is conducted at the present in the Standardization Organization such as IETF (Internet Engineering Task Force), aiming at actualizing an IPv6-based mobile IP.
The mobile IP actualizes terminal mobility by employing a layer-3 IP technology. To be specific, a home agent administering the mobile terminal manages a home-of-address (HoA) set in each mobile terminal in a network (home network) to which the home agent belongs and a care-of-address (CoA) set in a network (subnetwork) to which the mobile terminal moves, whereby continuity of the communications (seamless communications) is actualized by forwarding a transmission packet addressed to the home-of-address HoA of the mobile terminal to the care-of-address CoA.
For instance, in FIG. 17 showing a view of a system architecture of the prior art, an assumption is that a mobile terminal 100 (FIG. 19) administered by a home agent 200 (FIG. 18) in a home network 10, when getting located in a foreign network 30 connected via a wireless LAN, starts communications with a correspondent node (CN) 300, and thereafter moves to a foreign network 20. The following is a communication procedure to be made at that time.
(1) The correspondent node 300 starts performing the communications with the home-of-address HoA of the mobile terminal 100.
(2) A packet addressed to the home-of-address HoA is routed to the home network 10.
(3) The home agent 200 acting as a surrogate, the mobile terminal 100 not existing in the home network 10, captures the packet addressed to the home-of-address HoA, i.e., the packet addressed to the mobile terminal 100 and encapsulates the packet with a care-of-address CoA 2 defined as an address in the foreign network 30 where the mobile terminal 100 exists, thus forwarding the encapsulate packet (to the care-of-address CoA 2). With this encapsulation, the packet reaches the mobile terminal 100 in the foreign network 30.(4) Next, the mobile terminal 100, when moving to the foreign network 20, sends a registration request to the home agent 200.(5) The home agent 200 receiving the registration request changes the care-of-address CoA 2 associated with the home-of-address HoA to a care-of-address CoA 1. Thereafter, the packet from the correspondent node 300 is forwarded to the care-of-address CoA 1 in the foreign network 20. With this scheme, the packet reaches the mobile terminal 100 in the foreign network 20.
As described above, the mobile IP enables the continuous communications (seamless communications) even when the IP address is changed after the mobile terminal has moved to a (different) network. It should be noted that there must be redundant communication routes between the mobile terminal and the correspondent node always via the home agent when the mobile terminal exists in its moving destination, and hence route optimization is carried out in the great majority of cases. After carrying out the route optimization, the correspondent node transmits the packet not to the home-of-address HoA but directly to the care-of-address CoA. With this direct transmission, the communications can be performed via the optimized route between the mobile terminal and the correspondent node without via the home agent.
Further, a variety of systems (refer to Patent documents 1 through 4) are proposed as the prior arts related to the user mobility system. For example, [User Mobility Management Method in Personal Communication System] in Patent document 1 discloses a method of managing a subscriber number and terminal numbers of plural terminals usable by the user, and, when connected to the subscriber number, establishing a connection to an optimal terminal.
Patent Document 1
Japanese Patent Application Laid-Open Publication No. 10-191434
Patent Document 2
Japanese Patent Application Laid-Open Publication No. 2002-271369
Patent Document 3
Japanese Patent Application Laid-Open Publication No. 2002-344479
Patent Document 4
Japanese Patent Application Laid-Open Publication No. 2001-168906